Lubricating grease is provided to commercial customers in containers of varying sizes depending on the end use of the grease. An example of such container is a five gallon pail which typically holds about 35 pounds of grease. Larger containers include a 16 gallon keg containing 120 pounds of grease and a 55 gallon drum containing 400 pounds of grease. The kegs have been used with automatic grease systems mounted on very large material handling equipment of the type used in mining activities. In such use the keg is mounted on and travels with the piece of equipment. After a predetermined number of cycles of a component requiring lubrication, a grease pump is automatically activated to lubricate the component. Similarly, in manufacturing plants, a number of pieces of equipment can be tied to a drum of grease fitted with an automatically operated system that periodically dispenses grease to that equipment. The advantages of both these types of systems include the elimination of the need for constant tending of the equipment and a reduction in maintenance personnel requirements.
In such grease systems a pump is typically mounted atop the container. The pump has a pickup tube extending into the container to provide a suction point for the grease. The pickup tube terminates a short distance from the bottom of the container. As a consequence there always remains a thin layer of the normally very thick grease that cannot be pumped from the bottom of the container and could be lost as waste. The pump and pickup tube make up a pump assembly that can be moved from container to container as the grease therein is used up. This assembly is usually attached to a flexible discharge line so as to facilitate the change out of the grease containers.
The disposal of empty grease containers containing the residual amount of grease that cannot be reached by the pickup tube has given rise to environmental concerns. The grease can be considered a hazardous waste, making the proper disposal of the spent containers extremely costly and administratively burdensome. Cleaning the containers to a point that they could be disposed as normal, uncontaminated waste would be even more cost prohibitive. These environmental concerns led to the introduction of plastic liners in grease containers. Used in every size of container described above, the liners are a bag or sack that is installed in the container prior to filling. After the container is empty, the plastic liner can be removed from the container taking with it any residual grease. It is then possible to advantageously roll, scrape, or squeeze the residual grease out of the liner and then compact many liners into one container, thereby greatly reducing the amount of hazardous material generated. The liners offer the further advantages of reducing greatly the amount of waste grease from each container and allowing the empty containers to be reused or disposed easily. The liners have gained wide acceptance in the field.
Use of the liners has not come without some problems. The suction force of the grease systems is quite strong. It has been observed that as the grease level falls to close to the bottom of the containers, it is possible for the plastic liner to be drawn up from the bottom of the container and thereby be sucked up into the pickup tube. The slivers of plastic material thus generated cause tremendous damage to the grease pump components, many of which are manufactured to fine tolerances. Correcting the problem requires the time consuming job of disassembling the pump to find and remove the small pieces of plastic liner. It is also possible that pieces of the liner may pass through the pump and cause damage to the equipment being lubricated. The down time associated with these failures can be extremely costly to a high volume manufacturing facility or to a critical piece of mobile material handling equipment. This down time is particularly troublesome for automatic, unattended lubricating systems whose advantage is the elimination of the need for constant attention by maintenance workers. There exists a need then for a device to hold down the plastic liner of a grease container while at the same time allowing unimpeded flow through a grease pump pickup tube.
Attempts to address this kind of problem include U.S. Pat. No. 4,505,138 to Lang. This patent describes a trap for use in a top loading washing machine to prevent articles of clothing from entering the drain pump. The trap is located within the entrance to the hose connection between the tub and the pump.
U.S. Pat. No. 2,300,952, issued to Duthie, discloses a pump foot valve screen mounted in a pan to keep sand and small rocks from being drawn into the pump and causing undue wear and damage.
U.S. Pat. No. 1,945,824 to Saxe discloses a sand strainer for pumps. The strainer is intended to prevent the intake of sand into a pump by lowering the velocity of the incoming water. The construction of the strainer creates a trap that in combination with the low velocity water tends to keep sand out of the water being pumped.
Each of the inventions disclosed above, while useful for preventing the fouling of water pumps, are not acceptable for the pumping of grease or any other material of similar viscosity. The flow of such a material would be greatly impeded by the screens used in the strainers described above. Therefore, there exists a need for a system for use with a lined container that will maximize flow while preventing a plastic liner from being drawn into the pumping means.